Adjustable letoff for looms



May 18, 1948. w. H. WAKEFIELD 2,441,580

ADJUSTABLE LETOFF FOR LOOMS Filed Feb. 15, 1946 2 Sheets-Sheet 1 FIG. I

INVENTOR WALTER H. WAKE-751.0

ATTORNEY M y 8, 1948. w. H. WAKEFIELD 2,441,630

ADJUSTABLE LETOFF FOR LOOMS Filed Feb. 15, 946 2 Sheets-Sheet 2 H62 FIG. 3

V INVENTOR WALTER h. WAKEFELD ATTORNEY Patented May 18, 1948 UNITED STATES PATENT OFFICE ADJUSTABLE LETOFF FOR LOOMS Walter H. Wakefield, Worcester, Mass, assignor to Crompton & Knowles Loom Works, Worcester, Mass, a corporation of Massachusetts Application February 15, 1946, Serial No. 647,943

3 Claims. (Cl. 139-109) This invention relates to improvementsin letofl's for looms and it is the general object of the invention to provide a letoff usable with light or heavy weight warps.

A loom may at one time be used for weaving a light fabric the warp of which isunder relatively low tension and may at another time be used to weave a much heavier fabric the warp of which is under high tension. In a form of letoil which has gone into general use there is employed an escapement mechanism controlled by a brake the position of which is determined preferably by the whip roll. When light and medium weight fabrics are woven with a letoff of this type the escapement mechanism oscillates slowly enough to permit gradual turning of the warp beam when the brake is released. When heavy warps are employed however the tension is so high that the escapement mechanism is likely to oscillate too rapidly, thereby permitting rotation of the warp beam and reduction of warp tension at such a rate as to produce defects in the fabric.

It is an important object of my present invention to provide means by which the brake is caused to dampen rapid vibration of the escapement mechanism. As shown hereinafter I accomplish this result by holding one end of the brake shoe against the escapement mechanism, more particularly a lever forming part of it when the whip roll operates to move the greater part of the brake shoe out of the contact with the escapement lever. In this way the brake shoe is utilized not only to lock the letoff against operation, but also to restrain too rapid an oscillation of the escapement mechanism when heavy fabrics are being woven.

With these and other objects in view which will appear as the description proceeds, my invention resides in the combination and arrangement of parts hereinafter described and setv forth.

In the accompanying drawings, wherein a convenient embodiment of my invention is set forth,

Fig. 1 is a side elevation of a letoff mechanism having my invention applied thereto, the weight lever being shown in cross section,

Referring to Fig. 1, the loom frame III has extending rearwardly therefrom an upper support H on which a lever I2 is pivoted as at It. The lever 12 extends upwardly and has rotatably mounted thereon the whip roll l4 over which extends the warp W wound on the warp beam B.

Lever l2 cooperates with a horizontally rockable lever l5 moving about astationary vertical axis l6 and having an arm l1 normally exerting a rearward force on lever l2 tending to move the whip roll backwardly, or to the left as viewed in Fig. 1. Lever I5 is connected to a link or rod I8 connected to a lever is rocking in a vertical plane about a fixed axis 20 on support ll. Depending from lever I9 is a rod 2| which passes through the forward end of a brake lever 22 and has a collar 23 secured thereto below lever 22. A relatively strong compression spring 24 exerts a downward force on the right hand part of lever 22 and exerts an upward force on a sleeve 25 the position of which is adjusted by a nut 26 threaded on rod 2|.

Lever 22 rocks about a stationary stud 21 secured to a lower support 28 fixed to the loom frame. A small gear 23 rotates on stud 21 and meshes with a larger gear 30 secured to the beam B. Fast with respect to the small gear 29 is a gear 3| meshing with a pinion 32 rotatable about a fixed stud 33 on support 28. Fast with respect to pinion 32 is a gear 35 which meshes with a pinion 36 secured to a small stub shaft 31 rotatable in support 28. Keyed to the shaft 31 is an escapement or star wheel 38 notched as indicated in Fig. 1 for cooperation with the upper and lower lugs 39 and 40 respectively of an escapement lever ll pivoted as at 42 relatively. to the support 28. The escapement lever has a flange 45 which provides on the under side thereof a friction surface 46 for engagement with a brake shoe 41 pivoted as at 48 to the rear part of brake lever 22.

When the whip roll is in rearward position, a

- condition corresponding to relatively low warp Fig. 2 is an enlarged vertical section on line 2-2 of Fig. 1,

Fig. 3 is a side elevation looking in the direction of arrow 3, Fig. 2, showing the brake shoein non-locking but oscillation restraining position relatively to the escapement lever, and

Fig. 4 is a view similar to Fig. 3 but showing the shoe in looking relation with respect to the escapement lever.

tension, rod 2| will bein a relatively low position due to weights not shown on an arm 49 of lever 19 shown in sectionin Fig. 1. The spring 24 therefore exerts downward'force on the forward part of lever 22 and the shoe 4'! is held up against the surface 46 to lock the escapement I mechanism and prevent turning of the warp beam. As the whip roll moves forwardly dur-' ing locked condition of the warp beam incident to consumption of the warp by the weaving operation rod 2| is raised and the collar 23 eventually rocks lever 22 in a counter-clockwise direction as viewed in Fig. 1 to move the brake shoe downwardly away from the escapement lever. The latter is therefore free to oscillate under forces transmitted to its lugs by the escapement wheel The matter thus far set forth is of common construction and may be as des ribed in patent to Payne No. 2,184,059.

As already suggested,the letoif thus far described operates satisfactorily throughout" a rather wide range of warp tensions resulting from the weaving of fabrics of different weights. When a heavy fabric is being woven, however, resulting in the exertion of a high tensional force tending to turn the beam B, it is found that when the brake is released the star wheel 38 exerts such a large force on the escapement lever that the latter oscillates very rapidly with the result that there is a quick drop in. warp tension. If the whip roll is of considerable weight it may not respond instantaneously to this reduction in warp tension and a loose pick in the fabric will result.

In order to restrain or dampen the rate at which the escapement lever tends to oscillate under these conditions I provide means for causing Dart of the brake shoe to remain in,engagement with the friction surface 46 when the lever 22 rocks in such a direction as would otherwise efiect complete release of the escapement lever by the brake shoe.

The means for carrying my invention into effect is shown more particularly in Figs. 2 to 4, and comprises a screw stud 50 extending vertically through and adjustable in a rear extension 5! of lever 22. This screw is held in adjusted position with respect to the lever extension 5| by a lock nut 52. A coil spring 53 surround the upper end of stud 50 and rests on a slabbed nutlike part M of stud 50 adapted to receive a wrench. A stem 55 forming the upper part of the screw lies within the spring 53 to guide the latter, and the upper part of spring 53 enters a pocket 56 formed in the rear part of the shoe 1. The normal effect ofspring 53 is to exert an upward .force on the rear part of the brake shoe, tending to cause the latter to turn around its pivot 8, but this tendency of the spring depends upon the position of the adjusting screw, being relatively low when the screw is in downward position and being relatively high when the screw lsias been threaded upwardly through extension When a warp which exerts light tension is being woven the escapement lever will require very little if any dampening and under these conditions the spring 53 will be adjusted to exert a light upward force on the brake shoe, or if desired will exert no upward force. When a heavy warp is being woven, however, the screw 50 will be moved to a relatively high position with respect to the lever extension 5|, thereby causing spring 53 to exert an increased upward force on shoe When lever 22 is rocked in a counter-clockwise direction as viewed in Figs. 1 and 4 under these' conditions the forward part of the shoe will move down away from brake surface 46 to occupy some such position as indicated in Fig. 3. The rear part of the brake shoe, however, will be held up against the escapement lever by spring 53 and prevent the latter from oscillating too rapidly. It is to be understood that under these conditions the escapement lever 4| will move in a right and left hand direction with respect to the brake shoe, but the rear part of the latter will always be in position to restrain the escapement lever during some part at least of its oscillation.

From the foregoing it will be seen that I have provided simple means by which the tendency of the escapement lever to vibrate or oscillate can be "varied to adapt the letoff to the weight of the warp being used. The brake shoe which forms a normal part of the type of letoif mechanism to which the invention applies is utilized for this purpose. The brake shoe will have the greater part of its brake surface out of contact with the escapement lever when the whip roll is in forward position, but some part of the brake shoe will always be held against the escapement lever by spring 53 to restrain undue oscillation of the escapement lever when the adjusting screw 50 is in relatively high position incident to the weaving of heavy warp. When changingfrom light to heavy warp or vice versa the force exerted by the spring 53 can be adjusted readily by an appropriate adjustment of the screw 50 and the latter can be permanently mounted on the letoff mechanism. The upper extension 55 of stud 50 will hold the spring 53 in position when the stud is in low position and the dampening action on lever 4| has been either reduced or removed entirely.

Having thus described my invention, it will be seen that changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention and I do not wish to be limited to the details herein disclosed, but what I claim is:

1. In letoff mechanism for a loom having a warp beam tending to turn during loom operation and having an escapement lever operatively connected thereto which when free to oscillate enables the beam to turn but which when prevented from oscillating prevents turning of the beam, the rate of turning of the beam varying with the rate of oscillation of said lever, a brake lever movable from one position to another position during loom operation, a brake shoe pivoted intermediate the ends thereof on said brake lever and held thereby in braking position to prevent oscillation Of the escapement lever when said brake lever is in said one position thereof, said brake lever when in the other position thereof moving said brake shoe bodily away from braking position relatively to said escapement lever, and means interposed between the brake lever and one end of said brake shoe efl'ective to hold said end of the brake shoe against said escapement lever to dampen oscillation of the latter when said brake lever is in said other position thereof.

2. In letofl mechanism for a loom having a warp beam tending to turn during loom operation and operatively connected to an escapement lever which when free to oscillate from braking position with respect to the oscilv 2,441,eao

lating lever, thereby permitting the latter to oscillate, and means on the brake lever eflective when'the latter is in said other position thereof to hold one end of said brake against said escapement lever to dampen oscillation thereof.

3. In letoiI mechanism for a loom having a warp beam tending to turn during loom-operation and operatively connected to an escapement lever which when free to oscillate permits turning of the beam but which when held against oscillation prevents turning of the beam, a brake {or the escapement lever, a brake lever, means pivotally connecting the brake lever to the brake at a point on the latter intermediate the ends thereof, said brake lever when in one position holding said brake against the escapement lever to prevent oscillation thereof and said brake lever when in another position moving said brake in a direction away from braking position wlth'respect to the oscillating lever, thereby permitting the latter to oscillate, and means on the brake lever effective when the latter is in said other position thereof to hold one end of said brake against said escapement lever to dampen oscillation thereof, said last named means including an ad- 5 justable member on said brake lever movable to positions at different distances from said one end or said brake and a spring operatively interposed between said member and engaging said one end of said brake.

WALTER H. WAKEFIELD.

- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

